The proposed two-year project builds on an earlier exploratory study that investigated the prevalence of victimization among homeless men with mental illness. This project strives to enhance substance abuse research and practice by examining the relationship of trauma to substance use/misuse when controlling for other known predictors (i.e. mental health disorders, life stressors, and poor health). This study will collect data from approximately 290 homeless men concerning the extent to which they have experienced trauma in their lives and whether or not they abuse or misuse alcohol or other substances. Two agencies in Wake County, North Carolina, have agreed to assist in identifying candidates for the study. The cooperating agencies vary in the types of services they provide to homeless men, thereby helping to ensure a broad sample of the homeless male population. They include a homeless shelter that serves men who tend be actively using drugs, and an in-patient substance abuse treatment facility where men have short-term sobriety. This arrangement will provide a way to compare the similarities and/or differences in trauma histories for men at varying stages of substance abuse and homelessness. To make statements about the impact of trauma on substance abuse, the data will be used to fit a causal (i.e. time ordered, path analytic) model that incorporates a new perspective, a historical sequence, to factors hypothesized to predict substance abuse/misuse. This project will contribute to our understanding of the role of trauma in exacerbating the predisposition to abuse and misuse of alcohol and other substances, controlling for factors such as mental health disorders and life stressors. This project will also inform policy makers who direct practice so that services can more comprehensively and holistically serve those who use/misuse substances.